Dissemination of Multidrug-Resistant Commensal Escherichia coli in Feedlot Lambs in Southeastern Brazil
Dissemination of Multidrug-Resistant Commensal Escherichia coli in Feedlot Lambs in Southeastern Brazil
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DOI：
10.3389/fmicb.2019.01394
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发表时间：
2019-06-25
影响因子：
5.2
通讯作者：
Casella, Tiago
中科院分区：
文献类型：
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作者：
Gozi, Katia Suemi;Froes, Juliana Rodrigues;Casella, Tiago
抗生素耐药性（AR）是一个公共卫生问题，因为它限制了治疗人类和动物大肠杆菌感染的选择。在巴西，近年来羊肉市场不断增长，但有关绵羊 AR 的研究仍然很少。因此，本研究旨在调查饲养场期间从羔羊身上分离出的大肠杆菌中是否存在 AR。为此，在动物进入饲养场的第一天（第 0 天）和屠宰前的最后一天（第 42 天）收集断奶后 112 只 2 个月大的羔羊的粪便。在补充有 4 mg/L 头孢噻呋的麦康凯琼脂中选择分离株，并通过生化方法进行鉴定。通过纸片扩散和 PCR 对分离株进行抗菌药物敏感性测试，以研究系统发育组的基因、毒力决定因素以及对所测试的几种抗菌药物类别的耐药性。通过 S1-PFGE 和 Southern 印迹杂交阐明了检测到的 bla 基因的遗传定位。通过 XbaI-PFGE 和 MLST 方法对分离株进行分型。第 0 天从 8/112 (7.1%) 动物中分离出 78 株大肠杆菌，在第 42 天从 55/112 (49.1%) 动物中分离出 78 株大肠杆菌。由于几乎所有大肠杆菌 (97.4%) 中仅存在 fimH 作为毒力基因，而且 88.5% 属于系统群 B1 或 A，因此我们认为分离株代表肠道共生细菌。树状图将 78 个无毒力分离株分为七个簇，其中两个簇包含 50 个属于 ST/CC 1727/446 或 ST 3994 的大肠杆菌，在第 42 天回收，通常含有基因型 bla(CMY-2)-aac(3)-IIa -tetA-sul1-sul2-floR-cmlA。应特别注意 bla(CTX-M-15)（一种在全球范围内传播的基因）的存在，以及 bla(CTX-M-14)（巴西食用动物肠杆菌科细菌中迄今为止未检测到的基因）的存在。重要的是，这里检测到的携带 bla 基因的大肠杆菌谱系和质粒已被报道为人类感染源，无论是来自动物、食物还是环境，这引起了公共卫生问题。因此，饲养场中明显盛行两种携带重要 AR 基因的共生大肠杆菌，但羔羊也是携带重要 AR 基因的细菌的储存库，例如 bla(CTX-M-14) 和 bla(CTX-M-15)，这主要与抗菌治疗失败有关。
Antimicrobial resistance (AR) is a public health issue since it limits the choices to treat infections by Escherichia coli in humans and animals. In Brazil, the ovine meat market has grown in recent years, but studies about AR in sheep are still scarce. Thus, this study aims to investigate the presence of AR in E. coli isolated from lambs during feedlot. To this end, feces from 112 lambs with 2 months of age, after weaning, were collected on the first day of the animals in the feedlot (day 0), and on the last day before slaughtering (day 42). Isolates were selected in MacConkey agar supplemented with 4 mg/L of ceftiofur and identified by biochemical methods. Isolates were submitted to an antimicrobial susceptibility test by disc-diffusion and PCR to investigate genes for phylogenetic group, virulence determinants and resistance to the several antimicrobial classes tested. The genetic localization of the bla genes detected was elucidated by S1-PFGE followed by Southern blot-hybridizations. The isolates were typed by XbaI-PFGE and MLST methods. Seventy-eight E. coli were isolated from 8/112 (7.1%) animals on day 0, and from 55/112 (49.1%) animals on day 42. Since only fimH was present in almost all E. coli (97.4%) as a virulence gene, and also 88.5% belonged to phylogroups B1 or A, we consider that isolates represent intestinal commensal bacteria. The dendrogram separated the 78 non-virulent isolates in seven clusters, two of which comprised 50 E. coli belonging to ST/CC 1727/446 or ST 3994 recovered on day 42 commonly harboring the genotype bla(CMY-2)-aac(3)-IIa -tetA-sul1-sul2-floR-cmlA. Special attention should be given to the presence of bla(CTX-M-15), a worldwide gene spread, and bla(CTX-M-14), a hitherto undetected gene in Enterobacteriaceae from food-producing animals in Brazil. Importantly, E. coli lineages and plasmids carrying bla genes detected here have already been reported as sources of infection in humans either from animals, food, or the environment, which raises public health concerns. Hence, two types of commensal E. coli carrying important AR genes clearly prevailed during feedlot, but lambs are also reservoirs of bacteria carrying important AR genes such as bla(CTX-M-14) and bla(CTX-M-15), mostly related to antimicrobial treatment failure.